The present invention relates to pipe couplings and is specifically concerned with a new and improved coupling providing improved circumferential tensioning capability and better clamping action.
One well known type of pipe coupling for coupling end-to-end aligned pipes comprises a main body having a generally circular cross sectional shape which extends almost a full 360.degree. and terminates in opposed connecting flanges which are directed generally radially outwardly from the main body. Aligned apertures are provided in the connecting flanges for fastening means such as nuts and bolts. As the nuts and bolts are tightened to draw the connecting flanges together the resultant action impairs circumferential contraction to and tensioning of the main body thereby in turn creating radially inwardly directed clamping forces on the two pipe sections around the coupling.
In many applications a sufficiently tight coupling of the two pipes can be accomplished without a great deal of tightening. However, there are other situations where substantial circumferential tensioning forces are required. For example, where pipes are carrying fluids it may be important to have a tight, leak-resistant seal at the coupling. In the case of larger diameter pipes this means that relatively large tightening forces must be applied to the connecting flanges in order to attempt to impart the desired circumferential tension to the body of the coupling. Where these more demanding requirements are imposed, conventional pipe couplings may reach a point where the coupling begins to yield in such a way that increased tightening of the fastening means tends to tip one of the connecting flanges toward the other rather than imparting increased circumferential tension to the coupling body. In such a case increased tightening may even distort the coupling to a point where it is not suitable for use. Hence, where leakage of fluid passing through the coupled pipes is undesirable, conventional couplings may not be satisfactory. This means that additional measures must be taken in order to render the couplings effective and leak-resistant. Obviously these measures will involve additional complications and are generally wasteful of time, labor, materials, and money.
The present invention is directed to a new and improved pipe coupling having improved tensioning capability and which is well-suited for use in situations where tight coupling is specified. The present invention provides a pipe coupling which not only can be readily fabricated and installed but also can impart the required circumferential tension to render a coupling joint leak-resistant. The pipe coupling of the invention includes novel structural features associated with the connecting flanges whereby the fastening means may be tightened and the yielding which otherwise occurs is counteracted. In this way very substantial circumferential tension can be imparted to the coupling to achieve clamp forces capable of imparting a leak resistant character to a coupling joint even where the pipes are of larger diameter, for example four-inch pipes. The invention further possesses the advantage of requiring a small number of component parts and can be conveniently fabricated using standard manufacturing techniques.
The invention, in its presently preferred embodiment, comprises an extruded metal coupling having a generally circular main body which forms the coupling band and which extends almost a full 360.degree. around the axis of the coupling, terminating in opposed, generally radially directed, connecting flanges. Aligned apertures are provided in the connecting flanges and a headed bolt is passed through the aligned apertures, and a nut is run into the threaded shank of the bolt. Tightening of the nut and bolt is effective to draw the connecting flanges toward each other and thereby impart circumferential tension to the main body. Disposed radially outwardly of the connecting flanges are opposed abutment surfaces on the connecting flanges which are adapted to abut each other as the nut and bolt are increasingly tightened. When the two abutment surfaces abut each other, they form a fulcrum point about which continued tightening of the nut and bolt is effective to impart substantially increased circumferential tension to the coupling over that which existing prior to the abutment of the abutment surfaces.
In the preferred embodiment one abutment surface has a semi-circular shape as viewed axially of the coupling and the opposite abutment surface has a flat, planar shape. When they abut each other, the fulcruming action allows the semi-circular surface to roll on the flat surface and in this way the interaction between the abutment surfaces does not impair the effective tensioning of the coupling but rather promotes a much more effective tensioning than attainable with other couplings. The coupling is readily manufactured as an extruded metal, (aluminum, for example) so that the body of the coupling, the connecting flanges, and the abutment surfaces are all integral parts of a single piece. The extrusion may be cut to any desired length and the apertures drilled in the connecting flanges. Hence an economical construction is provided, yet one which may be readily installed and tightened without a complicated installation procedure.
Although the pipe coupling of the invention is well-suited to any application where pipes are to be coupled, it is particularly adapted for coupling larger diameter pipes, for example four inch pipes, where a leak-resistant joint is specified. For this purpose, additional sleeve elements may be disposed within the pipe coupling to impart a leak resistant characteristic to the joint. In the preferred embodiment these additional sleeve elements include a first metal sleeve element disposed within the main body of the coupling, an elastomeric sleeve element disposed within the first metal sleeve element, and a second metal sleeve element disposed within the elastomeric sleeve element. The second metal sleeve element is disposed in a central region of the coupling and overlaps both ends of the coupled pipes. The first metal sleeve element, the elastomeric sleeve element, and the main body of the pipe coupling extend axially in both directions beyond the axial ends of the second metal sleeve element so that when the coupling is installed and tightened the second metal sleeve provides a protection to the elastomeric sleeve element while the elastomeric sleeve element provides leak resistance for the joint.
In connection with the present invention a search was conducted in the U.S. Patent and Trademark Office which developed the following U.S. Pat. Nos.: 812,162; 2,227,551; 3,527,484; 3,834,744; 4,142,743; and 4,165,109. None of these patents discloses however the novel aspects of the present invention.